RU2406573C1 - Colour plus transparent multilayer coat - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to multilayer coats based on epoxy-acid transparent coats and to water-based basic or colour coats. This invention aims at increasing resistance to water, scratching and scuffing of transparent coats. For this, proposed composition comprises water-based film-forming composition that makes the basic coat and transparent film-forming composition that makes transparent top coat applied above the former. Basic coat is made from pigmented water-based film-forming composition. Said top coat is made from film-forming composition comprising polyepoxide and polyacid hardener. The latter is formed due to opening of the ring of poly basic acid anhydride hydroxyl groups of ether produced in reaction of polyhydric acid with surplus polyol. In said hardener, polyhydric acid has hydrocarbon chain comprising at least 20 adjacent carbon atoms arranged between groups of carbonic acid. Aforesaid ether can be produced by reaction between fat dicarboxylic acid and surplus polyol that contains more than two functional groups.

EFFECT: fine appearance of coat and higher resistance to ambient effects.

21 cl, 3 tbl, 5 ex

Description

FIELD OF THE INVENTION

This invention relates to multilayer “color plus transparent” coatings, and more particularly to multilayer coatings based on epoxy-acid transparent coatings and base or color coatings based on water.

BACKGROUND OF THE INVENTION

Color plus transparent coating systems, including applying a painted or pigmented basecoat to a substrate, followed by applying a transparent or unpainted topcoat to the basecoat, are becoming more and more popular as primary car finishes. The “color plus transparent” systems have remarkable brilliance and sharpness of the image, and the top transparent coating is especially important for these properties.

US patent No. 4,650,718 discloses transparent coatings based on polyacid and polyepoxide hardener. Although such transparent coatings provide excellent physical properties, such as resistance to acid etching, it is desirable to improve resistance to moisture, scratching and abrasion. An improved appearance over water-based basecoats is also desirable.

SUMMARY OF THE INVENTION

A multicomponent multilayer coating composition is disclosed comprising a pigmented film-forming composition serving as a main coating and a transparent film-forming composition serving as a transparent topcoat over a base coating in which

(a) a base coat is applied from a water-based pigmented film-forming composition, and

(b) a transparent outer coating is applied from a film-forming composition containing:

(i) polyepoxide and

(ii) a polyacid hardener formed by opening the ring of a polybasic acid anhydride with hydroxyl groups of a polyester obtained by reacting a polybasic acid with an excess of polyol, in which the polybasic acid has a hydrocarbon chain containing at least 20 adjacent carbon atoms between the acid groups.

Detailed description of the invention

All numbers used in this document expressing sizes, physical properties, technological parameters, amounts of ingredients, reaction conditions, etc. used in the description and claims are to be understood as being modified in all cases by the term “about”. Accordingly, unless otherwise indicated, the numerical values set forth in the following description and claims are approximations that may vary depending on the desired properties that are required to be obtained in accordance with the present invention. At least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical value should be considered at least in light of the number of indicated significant digits and using conventional rounding techniques. Also, all intervals disclosed herein should be considered to include the start and end values of the interval and encompassing any and all sub-ranges included therein. For example, the indicated interval "1-10", as you should assume, includes any and all sub-intervals between (and inclusive) the minimum value of 1 and the maximum value of 10; that is, all sub-intervals starting with a minimum value of 1 or more and ending with a maximum value of 10 or less, for example from 5.5 to 10. Also terms such as "applied on top", "applied on top", or "created on top" that are used herein, means applied or created on top, but not necessarily in contact with a surface. For example, a coating composition "deposited on top" of a substrate does not preclude the presence of one or more other coating films with the same or different composition located between the applied coating and the substrate. The molecular weight values used herein, or Mn or Mw, are determined by gel permeation chromatography using polystyrene as a standard. Also, the term "polymer", as used herein, includes oligomers, homopolymers and copolymers.

The base coat is applied from a pigmented, film-based, water-based composition. The water-based film-forming composition of the present invention can be any of the water-based compositions useful as basecoats in automobiles. Typically, such compositions include polymers with reactive functional groups, such as hydroxyl and carboxylic acid, and hardeners containing functional groups capable of reacting with the functional groups of the polymer, for example, an aminoplast.

Suitable film-forming polymers containing functional groups (also called crosslinkable film-forming resins) include acrylic polymers and copolymers, polyesters, polyurethanes, polyethers and mixtures thereof. These polymers can be self-crosslinking or crosslinked by reaction with suitable crosslinking materials included in the coating composition.

Suitable acrylic polymers and copolymers include copolymers of one or more alkyl esters of acrylic acid or methacrylic acid, optionally together with one or more other polymerizable ethylenically unsaturated monomers. Suitable alkyl esters of acrylic acid or methacrylic acid include aliphatic alkyl esters containing from 1 to 30, namely 4-18 carbon atoms in the alkyl group. Non-limiting examples include methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate. Other suitable copolymerizable ethylenically unsaturated monomers include vinyl aromatic compounds such as styrene and vinyl toluene; nitriles such as acrylonitrile and methacrylonitrile; vinyl and vinylidene halides such as vinyl chloride and vinylidene fluoride; and vinyl esters such as vinyl acetate.

The acrylic copolymer may contain hydroxyl functional groups, which are often incorporated into the polymer by incorporating one or more hydroxyl functional monomers into the reagents used to make the copolymer. Suitable hydroxyl functional monomers include hydroxyalkyl acrylates and methacrylates, preferably containing 2-4 carbon atoms in the hydroxyalkyl group, such as hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, caprolactone adducts with hydroxyl functional groups, and hydroxyalkyl acrylates, and the corresponding hydroxyalkyl acrylates. An acrylic polymer can be prepared using N- (alkoxymethyl) acrylamides and N- (alkoxymethyl) methacrylamides, which leads to self-crosslinking acrylic polymers.

Acrylic polymers can be prepared by water-emulsion polymerization methods and used directly to prepare a water-based coating composition or by polymerization methods in an organic solution using groups capable of forming salts, such as amine or acid groups. After neutralizing these groups with a base or acid, the polymers can be dissolved in an aqueous medium. Typically suitable crosslinkable film-forming resins have a weight average molecular weight of more than 2000 grams per mole, such as in the range of 2000 to 100000 grams per mole (as determined by gel permeation chromatography using polystyrene as a standard), and an equivalent hydroxyl mass in the range of 400 to 4000 grams on the equivalent. The term "equivalent weight" is a value calculated on the basis of the relative amounts of the various ingredients used in the creation of the specified material, and is based on the solids of the specified material. Relative amounts are those that result in the theoretical weight of the material in grams, namely, the polymer obtained from the ingredients, and give the theoretical number of specific functional groups that are present in the resulting polymer. The theoretical mass of the polymer is divided by the theoretical number to obtain an equivalent mass. For example, an equivalent hydroxyl mass is based on equivalents of the reaction side and / or terminal hydroxyl groups in the hydroxyl-containing polymer.

In addition to acrylic polymers, the resinous binder for the basecoat composition may be a polyester. Such polymers can be prepared in a known manner by condensation of polyols and polycarboxylic acids. Suitable polyols include ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, diethylene glycol, glycerin, trimethylolpropane, pentaerythritol and dimethylolpropionic acid.

Suitable polycarboxylic acids include succinic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid and trimellitic acid. In addition to polycarboxylic acids, the above functional equivalents of polycarboxylic acids, such as anhydrides, if any, or lower alkyl esters of polycarboxylic acids, such as methyl esters, can be used. Typically, an excess of an acid or polyol with an acidic functional group such as dimethylolpropionic acid is used in the synthesis of the polyester. The acidic functional group can be at least partially neutralized with a base, such as an organic amine, to dissolve or disperse the polyester in water.

Polyurethanes can also be used as the resinous binder in the basecoat. Polyurethanes that can be used include those formed by reacting polyols, including polymer polyols, such as ester polyols or acrylic polyols, such as those mentioned above, with a polyisocyanate such that the equivalent OH / NCO ratio is greater than 1: 1, so that free hydroxyl groups are present in the product. In addition, preferably the polyurethane contains free acid groups that can be at least partially neutralized with a base, such as an organic amine, to dissolve or disperse the polyurethane in water. An example of incorporation of acid groups into a polyurethane is the use of a mixed polyol, such as a polymer polyol and an acid functional polyol, such as dimethylol propionic acid.

The organic polyisocyanate that is used to make the polyurethane polyol may be an aliphatic or aromatic polyisocyanate, or a mixture of the two. Diisocyanates are preferred, although higher polyisocyanates may be used instead of or in combination with diisocyanates.

Examples of suitable aromatic diisocyanates are 4,4'-diphenylmethanediisocyanate and toluene diisocyanate. Examples of suitable aliphatic diisocyanates are linear chain aliphatic diisocyanates, such as 1,6-hexamethylene diisocyanate. Cycloaliphatic diisocyanates may also be used. Examples include isophorondiisocyanate and 4,4'-methylene bis (cyclohexyl isocyanate). Examples of suitable higher polyisocyanates are benzene 1,2,4-triisocyanate and polymethylene polyphenyl isocyanate.

Water-based basecoats in “color plus transparent” compositions are disclosed in US Pat. No. 4,403,003, and resinous compositions used in the preparation of these basecoats can be used in the practice of this invention. Also, water-based polyurethanes such as those obtained in accordance with US Pat. No. 4,147,679 can be used as the resinous binder in the basecoat.

A crosslinkable film-forming resin may have an acid number in the range of 5 to 100 mg KOH per g resin, namely 20-100 mg KOH per g resin. The acid number (the number of milligrams of KOH per gram of dry matter required to neutralize the acid functional groups in the resin) is a measure of the amount of acid functional groups in the resin.

Typically, a crosslinkable film-forming resin is present in an amount ranging from 40 to 94, namely, 50-80 wt.%, Based on the total solids weight of the resin of the topcoat composition. The water-based coating composition also includes one or more hardeners or crosslinking materials capable of reacting with a crosslinkable film-forming resin to form a crosslinked film. The crosslinking material may be present as a mixture with other components of a water-based coating composition (traditionally called a single-set system) or in a separate composition that is mixed with a crosslinkable film-forming resin several hours before applying the coating composition to a substrate (traditionally called a two-set system )

Suitable crosslinking materials include aminos and polyisocyanates and mixtures thereof. Applicable aminoplastic resins are based on the addition products of formaldehyde to a material carrying an amino or amido group. Condensation products obtained from the reaction of alcohols and formaldehyde with melamine, urea or benzoguanamine are the most common and are preferred herein. Although the aldehyde used is most often formaldehyde, other similar condensation products can be obtained from other aldehydes such as acetic aldehyde, crotonic aldehyde, acrolein, benzaldehyde, furfural, glyoxal and the like.

Condensation products of other amines and amides may also be used, for example, the condensation of an aldehyde with triazines, diazines, triazoles, guanadines, guanamines and alkyl and aryl substituted derivatives of these compounds, including alkyl and aryl substituted ureas and alkyl and aryl substituted melamines. Non-limiting examples of such compounds include N, N'-dimethylurea, benzourea, dicyandiamide, formaguanamine, acetoguanamine, glycoluryl, ammeline, 3,5-diaminotriazole, triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine and carbamoyl triazines NH ₃ R ₃ C ₃ N ₃ R ₃ C ₃ N ₃ R ₃ ) ₃ , in which X is nitrogen, oxygen or carbon, and R is a lower alkyl group containing from one to twelve carbon atoms, or a mixture of lower alkyl groups such as methyl, ethyl, propyl, butyl, n-octyl and 2- ethylhexyl. Such compounds and their preparation are described in detail in US Pat. No. 5,084,541.

Aminoplastic resins preferably contain methylol or similar alkylol groups, and in most cases at least a portion of these alkylol groups is esterified by reaction with alcohol. For this purpose, any monohydric alcohol may be used, including methanol, ethyl alcohol, propanol, butanol, pentanol, hexanol, heptanol, as well as benzyl alcohol and other aromatic alcohols, cyclic alcohols such as cyclohexanol, glycol monoesters, and halogen substituted or other substituted alcohols such as 3-chloropropanol and butoxyethanol. Aminoplastic resins are typically heavily alkylated with methanol or butanol.

The polyisocyanate, which is used as a crosslinking agent, can be obtained from several isocyanate-containing materials. Preferably, the polyisocyanate is a blocked polyisocyanate. Examples of suitable polyisocyanates include trimers derived from the following diisocyanates: toluene diisocyanate, 4,4'-methylene bis (cyclohexyl isocyanate), isophorone diisocyanate, isomeric mixture of 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanates, 1,6-hexamethylene diisocyanate tetramethylxylene diisocyanate and 4,4'-diphenylmethylene diisocyanate. In addition, blocked polyisocyanate prepolymers of various polyols, such as polyol esters, can also be used. Examples of suitable blocking agents include materials that can become unlocked at elevated temperatures, such as lower aliphatic alcohols, including methanol, oximes, such as methyl ethyl ketoxime, lactams, such as caprolactam, and pyrazoles, such as dimethylpyrazole.

Typically, the crosslinking material is present in an amount ranging from 5 to 50, namely 10-40 wt.%, Based on the total dry solids of the resin of the water-based coating composition.

The basecoat composition also contains pigments to give it color. Compositions having pigmentation with metal flakes are applicable for obtaining the so-called “glamorous metallic” finish mainly on the surface of automobile bodies. The proper orientation of the metallic pigments results in a dazzlingly shiny appearance with excellent flop effect, image clarity and strong gloss. Under the flop effect is meant a visual change in the brightness or lightness of the metal coating with a change in viewing angle, namely a change from 90 ° to 180 °. The larger the change, that is, from a light appearance to a dark one, the better the flop effect. The flop effect is important because it emphasizes the lines of a curved surface, such as a car body. Suitable metallic pigments include, but are not limited to, aluminum flakes, copper bronze flakes, and mica.

In addition to the metallic pigments, the basecoat compositions of the present invention may contain non-metallic colored pigments conventionally used in surface coating compositions, including inorganic pigments such as titanium dioxide, iron oxide, chromium oxide, lead and carbon chromate, and organic pigments such as phthalocyanine blue and phthalocyanine green. Typically, the pigment is included in the coating composition in an amount of about 1-80 wt.%, Based on the weight of the dry substances of the coating. Metallic pigment is used in an amount of about 0.5 to 25 wt.% By weight of the above filler.

Optionally, the basecoat composition may further comprise other materials known in the surface coating formulation technology. These may include surfactants, flow control agents, thixotropic additives, fillers, anti-gas agents, organic cosolvents, catalysts, and other common excipients. These materials may comprise up to 40 wt.% Of the total weight of the coating composition.

Basecoat compositions as well as subsequently coated clearcoat compositions may be applied to various substrates to which they adhere. Compositions can be applied by conventional means, including brushing, dipping, dyeing, spraying, etc., but most often they are applied by spray. Conventional atomization methods and equipment for spraying and spraying in an electrostatic field, such as electrostatic deposition in a cone, and either physical or automatic methods can be used.

Examples of substrates on which base coatings can be applied are metals, plastic, films on the surface of a metal, including elastomeric substrates and the like, which are located in motor vehicles. Substrates typically contain a primer, such as applied by electrolytic deposition, and optionally a spray-applied filler.

After the base coating composition is applied to the substrate, a film forms on the surface of the substrate. This is achieved by displacing the solvent, namely the aqueous and organic solvent, from the base coating film by heating or simply by a period of air drying. Preferably, only a heating step and for a short period of time is sufficient to ensure that the clearcoat composition is applied to the basecoat without dissolving the previous basecoat composition, that is, “intervention”. A suitable drying mode depends on the specific basecoat composition, on the humidity of the surrounding air with specific water-based compositions, but usually a drying time of about 1-5 minutes at a temperature of about 60-200 ° F (20-93 ° C) will be sufficient to ensure that so that mixing of the two coatings is minimal. At the same time, the basecoat film is sufficiently wetted in accordance with the composition of the transparent coating so that satisfactory adhesion between the coatings is achieved. More than one base coat and several transparent coatings can also be applied to create an optimal appearance. Typically, between previously applied coatings, a previously applied basecoat or a clearcoat is blown, that is, exposed to the environment for approximately 1-20 minutes.

The curing of both the basecoat and the clearcoat is usually achieved in one step by heating the multilayer coating to a temperature of from 120 to 160 ° C, preferably from 130 to 150 ° C for 15-40 minutes. If desired, the basecoat may first be cured by heating at the aforementioned temperatures and times, followed by application and subsequent curing of the transparent coating.

Typically, the base coat has a dry film thickness of 0.05 to 3, preferably 0.1 to 2 mils, and the transparent coating has a dry film thickness of 0.5 to 4.0, preferably 1.5 to 2.5 mils.

A transparent topcoat is applied from a film-forming composition comprising a polyepoxide and polyacid hardener.

Polyepoxide usually has a high content of epoxy functional groups (corresponds to a low equivalent mass of epoxide). More specifically, the polyepoxide of the present invention typically has an equivalent weight of epoxide in the resin dry matter of less than about 2000, and usually in the range of 150-1500.

Polyepoxide is usually relatively low molecular weight. More specifically, the polyepoxide of the present invention may have a number average molecular weight of not more than about 20,000, more preferably in the range of 500-20000.

The polyepoxides that can be used include epoxy-containing acrylic polymers, epoxy polycondensates such as polyglycidyl ethers of alcohols and phenols, polyglycidyl esters of polycarboxylic acids, some polyepoxide monomers and oligomers and mixtures of the foregoing.

The epoxy-containing acrylic polymer is a copolymer of an ethylenically unsaturated monomer having at least one epoxy group and at least one polymerizable ethylenically unsaturated monomer that does not contain an epoxy group.

Examples of ethylenically unsaturated monomers containing epoxy groups are those containing 1,2-epoxy groups and include glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether.

Examples of ethylenically unsaturated monomers that do not contain an epoxy group are alkyl esters of acrylic and methacrylic acid containing 1-20 atoms in the alkyl group. Specific examples of these acrylates and methacrylates include methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate. Examples of other copolymerizable ethylenically unsaturated monomers are vinyl aromatic compounds such as styrene and vinyl toluene; nitriles such as acrylonitrile and methacrylonitrile; vinyl and vinylidene halides such as vinyl chloride and vinylidene fluoride; and vinyl esters such as vinyl acetate.

The epoxy-containing ethylenically unsaturated monomer is preferably used in amounts of from about 20 to 90, more preferably from 30 to 70 wt.% Of the total amount of monomers used in the preparation of the epoxy-containing acrylic polymer. Of the remaining polymerizable ethylenically unsaturated monomers, preferably 10-80 percent, more preferably 30-70 wt.%, Of the total monomers are alkyl esters of acrylic and methacrylic acid.

An acrylic polymer can be prepared by solution polymerization methods in the presence of appropriate catalysts, such as organic peroxides such as tert-butyl perbenzoate, tert-amyl peracetate or ethyl 3,3-di (tert-amyl peroxy) butyrate or azo compounds such as benzoyl peroxide, N, N'-azobis (isobutyronitrile) or alpha, alpha-dimethylazobis (isobutyronitrile). The polymerization can be carried out in an organic solution in which monomers are soluble. Suitable solvents are aromatic solvents such as xylene and toluene, ketones such as methylamyl ketone, or ester solvents such as ethyl 3-ethoxypropionate. In another embodiment, the acrylic polymer may be prepared by aqueous emulsion or dispersion polymerization processes.

The epoxy polycondensates used are polyepoxides, that is, those having a 1,2-epoxy equivalence of more than 1, preferably more than 1, and up to about 5.0. A suitable example of such epoxides is polyglycidyl esters from the reaction of polycarboxylic acids with epihalohydrin, such as epichlorohydrin. Polycarboxylic acid can be formed by any method known in the art, and in particular by reacting aliphatic alcohols with anhydride, and in particular diols and alcohols with a large number of functional groups. For example, trimethylolpropane or pentaerythritol can react with hexahydrophthalic anhydride to produce a polycarboxylic acid, which then reacts with epichlorohydrin to form a polyglycidyl ester. Such compounds are especially useful because they are low molecular weight. Accordingly, they have a low viscosity and, therefore, coating compositions with a high solids content can be obtained with them. Also, the polycarboxylic acid may be an acrylic polymer with acidic functional groups.

Other examples of such epoxides are polyglycidyl ethers of polyphenols and aliphatic alcohols. These polyepoxides can be prepared by esterification of polyphenol or an aliphatic alcohol with an epihalohydrin, such as epichlorohydrin, in the presence of alkali.

Examples of suitable polyphenols are 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) and 1,1-bis (4-hydroxyphenyl) ethane. Examples of suitable aliphatic alcohols are ethylene glycol, diethylene glycol, pentaerythritol, thimethylol propane, 1,2-propylene glycol and 1,4-butylene glycol. In addition, cycloaliphatic polyols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-bis (hydroxymethyl) cyclohexane and hydrogenated bisphenol A can also be used.

In addition to the epoxy-containing polymers described above, certain polyepoxide monomers and oligomers may also be used. Examples of these materials are described in US Pat. No. 4,102,942 in column 3, lines 1-16. Specific examples of such low molecular weight polyepoxides are 3,4-epoxycyclohexylmethyl, 3,4-epoxycyclohexanecarboxylate and bis (3,4-epoxycyclohexylmethyl) adipate. These materials are aliphatic polyepoxides, which are epoxy-containing acrylic polymers. As mentioned above, epoxy-containing acrylic polymers are preferred because they lead to products having the best combination of coating properties, namely smoothness, gloss, durability and resistance to solvents. Such polymers have been found to be particularly useful in transparent coatings for “color plus transparent” applications.

The polyepoxide is present in the film-forming composition in amounts of from about 20 wt.% To 80 wt.%, And more preferably from 30 wt.% To 40 wt.%, Based on the total dry solids of the resin.

The composition of the present invention also includes a polyacid hardener formed by opening the polyacid anhydride ring with hydroxyl groups of a polyester obtained by reacting a polyacid with an excess of polyol in which the polybasic acid has a hydrocarbon chain of at least 20 adjacent carbon atoms between carboxylic acid groups. The polyacid hardener contains at least two acid groups. The acidic functional group is preferably a carboxylic acid, although acids such as phosphorus-based acid may be used. Preferably, the polyacid hardener is a carboxylic acid terminated material having an average of at least two, and preferably more than two, carboxylic acid groups per molecule.

Polyacid hardeners are ester-containing oligomers that are formed by opening the polyanhydride ring with the hydroxyl groups of the polyester obtained from the polyacid and the stoichiometric excess of the polyol.

Typically, in order to carry out the desired reaction, the polyanhydride and the polyester with hydroxyl functional groups are contacted together while mixing these two ingredients in a reaction vessel. Preferably, the reaction is carried out in an inert atmosphere, such as nitrogen, and in a solvent to dissolve the solid ingredients and / or reduce the viscosity of the reaction mixture. High boiling materials are examples of suitable solvents and include, for example, ketones such as methylamyl ketone, diisobutyl ketone, methyl isobutyl ketone; aromatic hydrocarbons such as toluene and xylene; as well as other organic solvents such as dimethylformamide and N-methyl-pyrrolidone.

The reaction temperature is preferably low, that is, not more than 135 ° C, preferably less than 120 ° C, and usually in the range of 70-135 ° C, preferably 90-120 ° C.

The reaction time may vary to some extent, mainly depending on the reaction temperature. Typically, the reaction time is from 10 minutes to 24 hours.

The equivalent ratio of anhydride to hydroxyl in the polyester with hydroxyl functional groups is preferably at least about 0.8: 1 (anhydride is considered monofunctional) to obtain maximum conversion to the desired half-ester. Relationships less than 0.8: 1 may be used, but such relationships result in increased formation of half esters with fewer functional groups.

Polyanhydrides that can be used to form the desired polyesters are those which, with the exception of the carbon atoms and the anhydride functional group, consist of about 2-30 carbon atoms. 1,2-Anhydride is preferred. Examples include aliphatic, including cycloaliphatic, olefin and cycloolefin anhydrides and aromatic anhydrides. Substituted aliphatic aromatic anhydrides are also included in the definition of aliphatic and aromatic, provided that the substituents do not adversely affect the reactivity of the anhydride or the properties of the resulting polyester. Examples of substituents include chloro, alkyl and alkoxy. Examples of anhydrides include succinic anhydride, metilsuktsinovy anhydride, dodecenyl succinic anhydride, oktadetsenilsuktsinovy anhydride, phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, alkilgeksagidroftalevye anhydrides such as methylhexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylene anhydride hlorendiktovy anhydride, itaconic anhydride, citraconic and maleic anhydride.

The polyacid hardener typically has an acid number of 30-300 mg KOH / g and a number average molecular weight of at least 1000, preferably 2000-10000.

Hydroxy functional polyesters are formed by the reaction of an excess of polyol with a polycarboxylic acid having a hydrocarbon chain containing at least 20 adjacent carbon atoms between carboxylic acid groups.

Among the polyols that can be used to produce the polyester include diols, triols, tetrols and mixtures thereof. Examples of polyols are preferably those which consist of 2-10 carbon atoms, namely aliphatic polyols. Specific examples include, but are not limited to, the following compounds: di-trimethylolpropane (bis (2,2-dimethylol) dibutyl ether); pentaerythritol; 1,2,3,4-butanetriol; sorbitol; trimethylolpropane; trimethylol ethane; 1,2,6-hexanetriol; glycerol; tris-hydroxyethyl isocyanurate; dimethylolpropionic acid; 1,2,4-butanetriol; TMP / epsilon-caprolactontriols; ethylene glycol; 1,2-propanediol; 1,3-propanediol; 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; neopentyl glycol; diethylene glycol; dipropylene glycol; 1,4-cyclohexanedimethanol and 2,2,4-trimethylpentane-1,3-diol. Preferably, the number of functional groups in the polyol is greater than 2, as for example in trimethylolpropane and pentaerythritol.

Examples of suitable polycarboxylic acids are linear or branched polycarboxylic acids having 2-4 carboxylic acid groups and containing at least 20, preferably at least 26, and more preferably 26-40 adjacent carbon atoms between carboxylic acid groups. Examples of suitable polycarboxylic acids are dimeric and polymeric polycarboxylic fatty acids, such as those sold under the trademark EMPOL, namely EMPOL 1008, EMPOL 1010, available from Cognis, and PRIPOL 1013, available from Uniquema, with EMPOL 1008 and PRIPOL 1013 being preferred.

The esterification reaction is carried out by methods known to those skilled in the chemical technology of polymers, and a detailed discussion is not considered necessary. Typically, the reaction can be carried out by combining the ingredients and heating to a temperature of from about 160 ° C to about 230 ° C. Other details of the esterification process are disclosed in US Pat. No. 5,468,802 in column 3, lines 4-20 and 39-45.

To introduce a hydroxyl functional group into the polyester, a stoichiometric excess of the polyol reacts with polycarboxylic acid. Typically, the equivalent OH / COOH ratio is from at least 2 to 1 and may be at least 3 to 1.

The polyacid hardener is present in the crosslinkable composition in amounts from about 0.5 to 50, preferably 5-20 wt.%, Based on the total solids of the resin.

The transparent coating compositions may be in the form of a one- or two-component system, depending on the reactivity of the polyepoxide material and the polyacid hardener.

In order to obtain improved scratch and abrasion resistance, the transparent coating composition may optionally contain inorganic particles. Inorganic particles can be ceramic materials, metallic materials, including metalloid materials. Suitable ceramic materials include metal oxides, metal nitrides, metal carbides, metal sulfides, metal silicates, metal borides, metal carbonates and mixtures of any of the foregoing. A specific non-limiting example of a metal nitride is, for example, boron nitride; a specific non-limiting example of a metal oxide is, for example, zinc oxide; non-limiting examples of suitable metal sulfides are, for example, molybdenum disulfide, tantalum disulfide, tungsten disulfide and zinc sulfide; non-limiting examples of suitable metal silicates are, for example, aluminum silicates and magnesium silicates, namely vermiculite.

A preferred inorganic particle is silica, including finely divided silica, amorphous silica, colloidal silica, alumina, colloidal alumina, titania, cesium oxide, yttrium oxide, colloidal yttrium oxide, zirconia, colloidal zirconia and mixtures any of the foregoing. In another embodiment, the present invention relates to curable compositions as previously described, in which the particles comprise colloidal silicon dioxide. As disclosed hereinabove, these materials may be surface treated or untreated.

The coating composition may contain precursors suitable for the in situ formation of silica particles by a gel-ash method. The coating composition according to the present invention may contain alkoxysilanes, which can be hydrolyzed to form particles of silicon dioxide in situ. For example, tetraethylorthosilicate can be hydrolyzed with an acid, such as hydrochloric acid, and condensed to form silica particles. Other suitable particles include surface-modified silica, such as those described in US Pat. No. 5,853,809 from column 6, line 51, to column 8, line 43.

It should be understood that since the curable composition of the invention is used as a transparent coating in a multicomponent multilayer coating composition, the particles should not substantially impair the optical properties of the curable composition. As used herein, “transparent” means that the curable coating has a BYK haze index of less than 50, as measured using the BYK / Haze Gloss tool.

Inorganic particles, if present in the composition, are present in an amount up to 10, preferably from 0.05 to 10, more preferably from 0.2 to 3 wt.%, Based on the total weight of the coating composition.

In addition to the above components, the coating compositions of the invention may contain one or more additional ingredients, such as auxiliary resins, including auxiliary hardeners, such as aminoplast, plasticizers, antioxidants, light stabilizers, anti-mildew agents, and fungicides, surfactants, and flow improvers or catalysts that are known in the art. These components, if any, are present in an amount up to 40% by weight, based on the total weight of the coating composition.

The components present in the curable coating composition of the present invention are usually dissolved or dispersed in an organic solvent. Organic solvents that can be used include, for example, alcohols, ketones, aromatic hydrocarbons, glycol ethers, esters, or mixtures thereof. The organic solvent is usually present in an amount of 5-80 wt.%, Based on the total weight of the composition.

The coating compositions of the present invention, after being applied to the substrate, have a good appearance, which is determined by the gloss and sharpness of the image and the scratch resistance, which is measured by the retention of gloss after the abrasion test, and good moisture resistance. Typical indicators are presented in the Examples.

EXAMPLES

The following examples are intended to illustrate the invention and should in no case be considered a limitation of the invention.

The following examples (A and B) demonstrate the preparation of two polyacid hardeners formed by opening the polybasic acid anhydride ring by hydroxyl groups of the polyester obtained by reacting the polycarboxylic acid with an excess of polyol. One of the polyesters was made with fatty dicarboxylic acid. The second polyester was made with adipic acid for comparative purposes.

Example A

This Example describes the preparation of an acidic functional polymer polyester used as a component in the thermosetting compositions of the present invention. The polyester was prepared from the following ingredients as described below.

Ingredients Mass parts (grams) Empol 10081 2239.7 Trimethylolpropane 1043.8 Butyl stannonic acid 5,0 Triphenylphosphite 5,0 Aromatic hydrocarbon solvent 1423.4 Hexahydrophthalic Anhydride 2439.9 n-amyl alcohol 800.6 1 Dimerdiacid is available from Cognis.

The polyester polymer was obtained in a round-bottomed four-necked flask equipped with a thermometer, a mechanical stirrer, a refrigerator, a dry nitrogen bubbler and a mantle heater. The first five ingredients were heated to 200 ° C and stirred in a flask until approximately 127 grams of distillate were collected and the acid number dropped below 1.5. Then the material was cooled to a temperature of 130 ° C and 712 grams of aromatic hydrocarbon solvent was added. Then hexahydrophthalic anhydride was added at 110 ° C and the mixture was kept at this temperature for 4 hours. The final product was a liquid having a non-volatile content of about 62% (as measured at 110 ° C. for one hour), and an acid number of 102, and a weight average molecular weight of 5542, as measured by gel permeation chromatography.

Example B (comparative)

This polymer was obtained in the same manner as the polymer described in Example A, except that Empol 1008 was replaced with adipic acid on an equivalent basis. The final product was a liquid having a non-volatile content of about 62% (as measured at 110 ° C. for one hour), an acid number of 63, and a weight average molecular weight of 2253, as measured by gel permeation chromatography.

The following Examples are various basecoat compositions. Example 1 was a water-based basecoat.

Examples 2 and 3 were presented for comparative purposes and were base coatings based on an organic solvent, as described in US patent No. 5,898,052.

Example 1

The water-based basecoat was an industrial product obtained from PPG Industries as HWT 36427. The basecoat composition was composed of polyester polyol, acrylic polyol and amine hardener.

Examples 2 and 3 (comparative)

Solvent-based basecoats were taken from US Pat. No. 5,898,052, Example 1 from Table 2 and Example 3 from Table 2. The primer compositions were as follows.

Example 2 (Comparative) (US Patent No. 5,898,052, Example 1, Table 2)

Ingredient Dry weight (grams) Weight (grams) Acrylic component according to patent (A-i) GMA (glycolmethacrylate) 39.90 57.00 Crosslinking agent, component according to patent (B-ii) acid / OH 30.10 43.00 Component according to (c-i) Cymel 202 30.40 38.00 Alpate 7670NS ¹ 9.98 15.01 Methylisobutylketone - 109.80 Total 110.38 262.81 ¹ Aluminum paste obtained from Toyal Europe.

Example 3 (Comparative) (US Patent No. 5,898,052, Example 3, Table 2)

Ingredient Dry weight (grams) Weight (grams) Acrylic component in accordance with patent (A-i) GMA 39.90 57.00 Crosslinking agent, component according to patent (B-ii) Acid / OH 30.10 43.00 Component According to Patent (c-ii) Cymel 370 ¹ 29.92 34.00 Alpate 7670NS 9.98 15.01 Methylisobutylketone - 119.05 Total 109.90 268.06 ¹ Melamine formaldehyde resin obtained from CYTEC Industries, Inc.

The following Examples provide clear topcoat compositions based on polyepoxide-polyacid hardeners. In Example 4, the polyacid of Example A is used as a hardener, and in Example 5, the polyacid of Example B is used as a hardener.

Example 4

A clear surface coating composition was prepared from the following ingredients

Ingredient Dry weight (grams) Weight (grams) SET 1 Dowanol DPM® ¹ - 5.84 n-pentylpropionate - 11.00 Tinuvin 328 ² 2.54 2.54 Treated Colloidal Silica ³ 0.50 3.47 Acrylic polymer ⁴ 38.69 60.45 ERL-4221 ⁵ 6.00 6.00 Cymel 202 ⁶ 5.00 6.25 Q-293 ⁷ 0.37 0.37 Byk 331 ⁸ 0,03 0,03 50% Dynoadd F-1 solution ⁹ 0.16 0.33 SET 2 n-pentylpropionate - 8.38 Isobutyl acetate - 6.64 Colloidal Silica Dispersion ¹⁰ 3.79 10.11 Acid Crosslinking Agent ¹¹ 29.42 40.58 Acid Crosslinking Agent of Example A 18.00 28.59 Catalyst ADMA 12 ¹² 1.99 1.99 TOTAL 106.49 192.57 ¹ Solvent obtained from Dow Chemical Co.
² UV absorber obtained from Ciba Additives.
³ "Silica B" is prepared as described in US Pat. No. 11 / 145,812, issued June 6, 2005, incorporated herein by reference.
⁴ Polymer consisting of 60% glycidyl methacrylate, 30.8% n-butyl methacrylate, 0.2% methyl methacrylate, 7% styrene and 2% alpha-methyl styrene dimer. The Mw of a polymer having an equivalent mass of epoxy 237 is about 2500, based on solids. The polymer is 64% solids in n-pentylpropionate.
⁵ Cycloaliphatic diepoxide obtained from Dow Chemical Co.
⁶ Melamine formaldehyde resin obtained from CYTEC Industries, Inc.
⁷ light stabilizers derived from New York Fine Chemicals.
⁸ Polyether / dimethylpolysiloxane copolymer obtained from Byk Chemie.
⁹ Silicone-free polymer obtained from Dyno Cytec, which was diluted to a 50% solution in a mixture of n-butyl acetate and Butyl Cellosolve® Acetate 1/1, obtained from Dow Chemical Co.
^{10 The} finely divided silica HDK® H30LM obtained from Wacker Chemie AG is dispersed in a polymer consisting of 55% 4-methylhexahydrophthalic anhydride, 23% hexahydrophthalic anhydride and 22% trimethylol propane in n-butyl acetate, with an Mw of about 650 and acid equivalent weight based on solids, at 72.5% solids.
¹¹ A polymer consisting of 55% 4-methylhexahydrophthalic anhydride, 23% hexahydrophthalic anhydride and 22% trimethylol propane in n-butyl acetate, with an Mw of about 650 and an acid equivalent weight of 205, based on dry matter, at 72.5% solids.
¹² Amine obtained from Albemarle Corp.

Example 5 (Comparative)

A clear topcoat composition was prepared from the following ingredients

Ingredient Dry weight (grams) Weight (grams) SET 1 Dowanol DPM® - 5.84 n-pentylpropionate - 11.00 Tinuvin 328 2.54 2.54 Treated Colloidal Silica 0.50 3.47 Acrylic polymer Project 4 39.94 62.41 ERL-4221 6.00 6.00 Cymel 202 5.00 6.25 Q-293 0.37 0.37 Byk 331 0,03 0,03 50% Dynoadd F-l solution 0.16 0.33 SET 2 n-pentylpropionate - 8.38 Isobutyl acetate - 6.64 Fine silica dispersion 3.79 10.11 Acid Crosslinking Agent Pr. 4 33.13 45.70 Acid Crosslinking Agent of Example B 13.04 21.03 Catalyst ADMA 12 1.99 1.99 TOTAL 106.49 192.09

The following Examples present pigmented clear multilayer coatings using water-based pigmented basecoat and clear topcoat compositions of Examples 4 and 5.

The transparent film-forming compositions of Examples 4 and 5 were sprayed onto water-based pigmented basecoats, as shown in the tables below, to obtain multilayer “color plus transparent” coatings on top of the electroplated primed steel panels. The panels were cold rolled ACT steel panels (10.16 cm by 30.48 cm) plated with ED6060 obtained from ACT Laboratories, Inc. The panels were coated with either HWB9517, a black pigmented water-based basecoat obtained from PPG Industries, or HWT36427, a silver pigmented water-based basecoat, obtained from PPG Industries. The basecoats were sprayed onto electroplated steel panels at ambient temperature (approximately 70 ° F (21 ° C)). The dry film thickness for the basecoat was set from about 0.5 to 0.7 mils (about 12-17 micrometers). The basecoat panels were dehydrated for 5 minutes at 176 ° F (80 ° C) until a clear coating was applied.

The basecoat compositions (Examples 1-3) were sprayed onto primed galvanized coated steel panels at ambient temperature (approximately 70 ° F (21 ° C)). The panels used were ACT cold-rolled steel panels (10.16 cm by 30.48 cm) plated with ED6060 obtained from ACT Laboratories, Inc. For the basecoat, a dry film thickness of about 0.6 to 0.8 mils (about 16-19 micrometers) was set. The basecoat panels were dried for 5 minutes at 176 ° F (80 ° C) until a clear coating was applied.

The transparent coating composition of Example 4 was sprayed onto the basecoat coated panels at ambient temperature with two coatings with an ambient blow between applications. The installed dry film thickness of the clear coat was 1.7 mils (approximately 43 micrometers). The coatings were left in the air for rapid evaporation at ambient temperature before being placed in the oven. The panels were dried for thirty minutes at 260 ° F (127 ° C) to completely cure the coating (s). The panels were tested for appearance indicators (such as 20 ° gloss, DOI, color, and flop index). The results are presented below.

Table 1 Appearance indicators Example
Basecoat / Clearcoat Flop index ^l 20 ° Gloss ² DOI ³ 1/4 13.89 91 93 2/4 7.56 86 83 3/4 7.66 86 83 ¹ The indicator corresponding to the ratio of the mirror reflection coefficient to the angular, obtained using a multi-angle spectrophotometer X-Rite MA68II. The higher the number, the better the flop effect.
² Gloss at 20 ° was measured using a NOVO-GLOSS statistical glossometer obtained from Gardco.
³ DOI (Image Clarity) was measured using a DOI / HAZE meter, Model 807A, obtained from Tricor Systems, Inc.

The data presented in Table 1 above shows that the multilayer basecoat / clearcoat of the present invention, in which the clearcoat is based on a polyepoxide-polyacid hardener and is applied over a water-based topcoat, has an excellent appearance compared to multi-layer coatings, in which a transparent coating is applied over a solvent-based basecoat.

The following Examples relate to multilayer pigmented clear coatings in which the clear topcoat compositions of Examples 4 and 5 are applied over a water-based pigmented basecoat.

Each composition of the transparent coatings of Examples 4 and 5 was automatically sprayed onto a basecoated panel at ambient temperature with two coatings blowing in the environment between applications. The installed dry film thickness of the clear coat was 1.7 mils (approximately 43 micrometers). All coatings were left to purge with air at ambient temperature before curing. The panels were heated in an oven for thirty minutes at 260 ° F (127 ° C) to completely cure the coating (s). The panels were tested for performance such as scratch resistance (Amtec car wash and Atlas abrasion resistance tester) and moisture resistance (140 ° F (60 ° C) and 110 ° F (43 ° C) in a QCT cure tester and 100 ° F (38 ° C) in a humid chamber). The properties of the coatings are presented in the tables below.

table 2 Scratch resistance Initial gloss 20 ° Crockemeter ¹ (Scratch 20 ° Gloss) Car Wash ² (Scratch 20 ° Gloss) Cycles Transparent coating Base coverage 10 cycles 10 twenty thirty 40 Example 4 HWB9517 black 85 51 51 23 10 5 Example 5 HWB9517 black 85 60 42 17 7 four ¹ Test on the device for measuring abrasion resistance was carried out in the following way:
1. The Atlas AATCC Crockemeter acrylic finger, model CM-5, manufactured by Atlas Electric Devices Company, Chicago, Ill., Was coated with a two inch by two inch (3 cm by 3 cm) piece of felt obtained from Atlas Electric Devices, and a piece of nine (9) micron polishing paper of two inches by two inches (3 cm by 3 cm) size, obtained from 3 M Company.
2. The coated scraper panel was rubbed 10 times (10 double friction) using a Crockmeter.
3. The test was repeated at least once with the replacement of felt fabric and polishing paper after each test.
4. 20 ° gloss was measured using the above Novo-Gloss gloss meter on both the non-scratched part of the panel and the scratched parts of the panel. Gloss difference was a measure of surface hardness. The smaller the difference, the greater the surface hardness.
² A car wash test was performed using an automatic car wash for Amtec vehicles. This test method used consisted of an Amtec Car Wash Lab Apparatus for the implementation of a test protocol and a washing suspension of 30 grams of Sikron SH200 gravel per 20 liters of tap water as described in DIN 55668. The 20 ° gloss values were recorded using a Novo-Gloss ™ statistical gloss meter from Gardco®. The Amtec Car Wash Lab Apparatus for implementing the test report and the Sikron SH200 were obtained from Amtec Kistler GmbH.

The experimental data in Table 2 show that the multilayer coatings of the present invention have improved scratch resistance with respect to the comparative example when determined by a car wash test.

Table 3 Moisture resistance Transparent coating Base coverage 4 days 140 ° F QCT 4 days 110 ° F QCT 10 days 100 ° F / 100% rel. ow Camera Example 4 HWT36427 silver 8 several
Slight turbidity 10 No haze 10 No haze Example 5 HWT36427 silver 8 Frequent
Slight turbidity 10 No haze 10 No haze Example 4 HWB9517 black 10 No haze 10 No haze 10 No haze Example 5 HWB9517 black 10 No haze 10 No haze 10 No haze

Bubble rating is in accordance with ASTM D714-87. No. 10 shows the absence of bubbling. No. 8 shows the smallest bubbles easily visible to the naked eye. The frequency of bubble formation is marked as frequent, medium frequency, moderate and somewhat. Assessment for turbidity is visual observation.

The experimental data presented in Table 3 show that the multilayer coatings of the invention and comparative example have good moisture resistance, and the multilayer coatings of the invention have better moisture resistance, determined by a 4-day test at 140 ° F.

Although specific embodiments of the present invention have been described above for purposes of illustration, one skilled in the art will appreciate that numerous changes may be made in the details of the present invention without departing from the invention as defined in the appended claims.

Claims (21)

1. A multicomponent multilayer coating composition comprising a pigmented film-forming composition serving as a base coating and a transparent film-forming composition serving as a transparent topcoat over the base coating, in which
(a) a base coat is applied from a water-based pigmented film-forming composition, and
(b) a clear topcoat is applied from a film-forming composition comprising
(i) polyepoxide and
(ii) a polyacid hardener formed by opening the ring of a polybasic acid anhydride with hydroxyl groups of a polyester obtained by reacting a polybasic acid with an excess of polyol, in which the polybasic acid has a hydrocarbon chain containing at least 20 adjacent carbon atoms between carboxylic acid groups. 2. The composition according to claim 1, in which the pigmented film-forming composition on a water basis includes
(a) a polymer with reactive functional groups and
(b) a hardener with functional groups capable of reacting with functional groups (a). 3. The composition according to claim 2, in which the functional groups (a) are selected from hydroxyl and carboxylic acid. 4. The composition according to claim 2, in which the hardener is an amino plastic. 5. The composition according to claim 1, in which the polyepoxide is a copolymer of glycidyl acrylate or glycidyl methacrylate with at least one other copolymerizable monomer. 6. The composition according to claim 1, in which another copolymerizable ethylenically unsaturated monomer includes an alkyl ester of acrylic or methacrylic acid. 7. The composition according to claim 1, in which the polyepoxide has a number average molecular weight of 500-20000 and an equivalent weight of the epoxide of 150-1500, based on the solids of the resin. 8. The composition according to claim 1, in which the polybasic acid has a hydrocarbon chain containing at least 20 adjacent carbon atoms between carboxylic acid groups. 9. The composition according to claim 1, in which the polybasic acid is a fatty dicarboxylic acid. 10. The composition according to claim 9, in which the fatty dicarboxylic acid has a hydrocarbon chain of 26-40 adjacent carbon atoms between the carboxylic acid groups. 11. The composition according to claim 1, in which the polyol has a number of functional groups greater than 2. 12. The composition according to claim 11, in which the polyol is selected from trimethylolpropane and pentaerythritol. 13. The composition according to claim 1, in which the hardener has an acid number of 30-300 mg KOH / g 14. The composition according to claim 1, in which the hardener has a number average molecular weight of at least 1000. 15. The composition according to claim 1, in which
(i) is present in the film-forming composition (b) in an amount of 20-80 wt.%, and
(ii) is present in an amount of 0.5-50 wt.%;
mass percentages are based on the total solids of the resin. 16. A multicomponent multilayer coating composition comprising a pigmented film-forming composition serving as a base coating and a transparent film-forming composition serving as a transparent topcoat over the base coating, in which
(a) a base coat is applied from a water-based pigmented film-forming composition, and
(b) a clear topcoat is applied from a film-forming composition comprising
(i) polyepoxide, and
(ii) a polyacid hardener formed by opening the ring of an anhydride of polybasic acid with hydroxyl groups of a polyester obtained by reacting a fatty dicarboxylic acid with an excess of a polyol having a number of functional groups greater than 2. 17. The composition according to clause 16, in which the fatty dicarboxylic acid contains a hydrocarbon chain of 26-40 adjacent carbon atoms between the carboxylic acid groups. 18. The composition according to clause 16, in which the polyol is selected from trimethylolpropane and pentaerythritol. 19. The composition according to clause 16, in which the hardener has an acid number of 30-300 mg KOH / g 20. The composition according to clause 16, in which the hardener has a number average molecular weight in the range of 2000-10000. 21. The composition according to clause 16, in which
(i) is present in the film-forming composition (b) in an amount of 30-40 wt.%, and
(ii) is present in an amount of 5-20 wt.%;
mass percentages are based on the total dry solids of the resin in (b).